<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2016, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT	MIT License
 * @link    https://codeigniter.com
 * @since    Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Database Cache Class
 *
 * @category    Database
 * @author        EllisLab Dev Team
 * @link        https://codeigniter.com/user_guide/database/
 */
class CI_DB_Cache
{

    /**
     * CI Singleton
     *
     * @var    object
     */
    public $CI;

    /**
     * Database object
     *
     * Allows passing of DB object so that multiple database connections
     * and returned DB objects can be supported.
     *
     * @var    object
     */
    public $db;

    // --------------------------------------------------------------------

    /**
     * Constructor
     *
     * @param    object &$db
     * @return    void
     */
    public function __construct(&$db)
    {
        // Assign the main CI object to $this->CI and load the file helper since we use it a lot
        $this->CI =& get_instance();
        $this->db =& $db;
        $this->CI->load->helper('file');

        $this->check_path();
    }

    // --------------------------------------------------------------------

    /**
     * Set Cache Directory Path
     *
     * @param    string $path Path to the cache directory
     * @return    bool
     */
    public function check_path($path = '')
    {
        if ($path === '') {
            if ($this->db->cachedir === '') {
                return $this->db->cache_off();
            }

            $path = $this->db->cachedir;
        }

        // Add a trailing slash to the path if needed
        $path = realpath($path)
            ? rtrim(realpath($path), DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR
            : rtrim($path, '/') . '/';

        if (!is_dir($path)) {
            log_message('debug', 'DB cache path error: ' . $path);

            // If the path is wrong we'll turn off caching
            return $this->db->cache_off();
        }

        if (!is_really_writable($path)) {
            log_message('debug', 'DB cache dir not writable: ' . $path);

            // If the path is not really writable we'll turn off caching
            return $this->db->cache_off();
        }

        $this->db->cachedir = $path;
        return TRUE;
    }

    // --------------------------------------------------------------------

    /**
     * Retrieve a cached query
     *
     * The URI being requested will become the name of the cache sub-folder.
     * An MD5 hash of the SQL statement will become the cache file name.
     *
     * @param    string $sql
     * @return    string
     */
    public function read($sql)
    {
        $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
        $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);
        $filepath = $this->db->cachedir . $segment_one . '+' . $segment_two . '/' . md5($sql);

        if (FALSE === ($cachedata = @file_get_contents($filepath))) {
            return FALSE;
        }

        return unserialize($cachedata);
    }

    // --------------------------------------------------------------------

    /**
     * Write a query to a cache file
     *
     * @param    string $sql
     * @param    object $object
     * @return    bool
     */
    public function write($sql, $object)
    {
        $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
        $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);
        $dir_path = $this->db->cachedir . $segment_one . '+' . $segment_two . '/';
        $filename = md5($sql);

        if (!is_dir($dir_path) && !@mkdir($dir_path, 0750)) {
            return FALSE;
        }

        if (write_file($dir_path . $filename, serialize($object)) === FALSE) {
            return FALSE;
        }

        chmod($dir_path . $filename, 0640);
        return TRUE;
    }

    // --------------------------------------------------------------------

    /**
     * Delete cache files within a particular directory
     *
     * @param    string $segment_one
     * @param    string $segment_two
     * @return    void
     */
    public function delete($segment_one = '', $segment_two = '')
    {
        if ($segment_one === '') {
            $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
        }

        if ($segment_two === '') {
            $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);
        }

        $dir_path = $this->db->cachedir . $segment_one . '+' . $segment_two . '/';
        delete_files($dir_path, TRUE);
    }

    // --------------------------------------------------------------------

    /**
     * Delete all existing cache files
     *
     * @return    void
     */
    public function delete_all()
    {
        delete_files($this->db->cachedir, TRUE, TRUE);
    }

}
